Method of and explosive for blasting deep well holes



Patented Feb. 27, 1934 UNITED STATES PATENT oi-FicE METHOD OF AND EXPLOSIVE FOR BLAST ING DEEP WELL HOLES No Drawing. Application December 9, 1931 d Serial No. 579,988

12 Claims. (01. 102-45) My invention relates to improvements in methods of, and explosives for, blasting deep well holes. It is applicable where there is a heavy pressure of air, water, oil or other gas or liquid upon the explosive used. More particularly it relates to blasting oil and gas wells surely and effectively and to providing improved explosive assemblies for the various purposes named.

Well holes as deep as 9000 feet' are known and in deeper ones are likely in the future. High temperatures are usually encountered. It is obvious, therefore, that severe pressure and temperature conditions are imposed upon explosives in this field of use.

Ordinarily gelatinous explosives are used and this invention is restricted to high grade gelatinous explosives in which the content of nitroglycerine or other liquid explosive is or, greater. In this work blasting efiectiveness is :0 dependent upon the detonating wave of the gelatinous explosive propagating throughout the entire charge at the maximum rate of detonation. Instances of poor effectiveness and partially burning charges have been known with '35 the types of gelatinous explosives nbw in use.

It is known in the, explosives industry that gelatinous explosives lose their propagation sensitiveness rapidly when subjected to a vacuum,

high pressure, high temperatures or rapid tem-' perature changes. Even too much pressure in the normal packing operation at the factory can result in a product of lowered sensitivityto propagation. Obviously, in a long vertical charge even the weight of the gelatinous explosive upon itself can result in a similar condition.

Each of the several conditions mentioned above, to which gelatinous explosives are subjected is thought to exert its effect through the removal of air from the explosive. For instance, if a gelatinous explosive having high propagation sensitiveness is submitted to any of the conditions mentioned it will be found to have increased in density and to have become less sensitive to propagation. A gelatinous explosive is conceived to have air stirred into it during manufacture and this air exists in the finished product in the form of minute bubbles. The plastic walls of these bubbles collapse under the influence of the severe conditions cited above and air is forced from the explosive.

From the very nature of gelatinous explosives and the causes and effects cited, it seemed that the gelatinous explosive itself could not be modifled to obviate this difficulty. Accordingly, my no object, which is to provide more positive, continuous, brisant explosive action from gelatinous explosives and to assure a higher order of deto- ,1 am of the opinion that any explosive has a critical pressure above which its propagation sensitiveness is affected and insuflicient aeration may be a partial cause at least. However, in granular, non-gelatinized explosives or in semigelatins the walls of the air cells are solid materials largely and not so easily collapsed as is the case when the cell walls consist preponderantly of plastic gelatinized nitrocellulose.

Accordingly, my problem was answered by, and my invention consists in, providing a core of granular, non-gelatinized or semi-gelatinized dynamite in my gelatin of 50% or more nitroglycerin content or liquid substitutes. Ordinarily' such explosives would not be satisfactory for deep well holes because of relatively poor resistance to the penetration of such liquids as water or oil, because their non-plastic nature might prevent their shape adapting itself to fill torpedoes or the holes thoroughly, because of lower density and in somcases of greater hazard in handlingunder severe conditions.

The explosive within the types ,mentioned which has the greatest propagation sensitiveness is the so-called straight nitroglycerine dynamite. Accordingly, I prefer to use within my gelatins, a core of straight nitroglycerine dynamite. However, other straight dynamites are almost equally satisfactory. While I have expressed a preferred method, it will be understood that my invention includes a core of any non-gelatinous or semi-gelatinous explosive in a gelatinous explosive of 50% or more nitroglycerine content or I equivalent explosive, whether said equivalent is liquid in itself or liquid because it is soluble in nitroglycerine. For instance, trinitrotoluene is a solid at ordinary temperatures, yet it may be dissolved in nitroglycerine to form a liquid mass.

I am aware that cores of more sensitive explopurpose.

My gelatinous explosive may be in any diameter or length. My core may be from diameter up and of such length as to equal that of the gelatinous explosive or any lesser or greater length. For instance, if only one-third of the length of gelatinous explosive were cored, considerable of my desired efiects would result. While I find a core of approximately /2" in diameter or .196 sq. in. in cross sectional area to be suitable, it is to be understood that the invention is not limited with respect to the particular cross section or arrangement of the core nor to the cross sectional shape of said core. Any desired cross sectional shape may be employed, such as round, square, triangular or other polygonal shape. Irrespective of the shape employed, a cross sectional arrangement of approximately .196 sq. in. is found to be suitable although not limiting.

I prefer to have the core in the vicinity of the center of the gelatinous explosive because it is there best protected from 'ater or oil and against handling hazards in cases where the core might be more sensitive to mechanical effects than the gelatinous explosive itself. In such a central position the core offers least resistance to the conformation of the gelatinous explosives to the torpedo or well hole. .Further, it gives greatest assurance of the core lining up most effectively. However, the core may be in any desired position in the gelatinous explosive. For the best practical purposes I could make limitations as to the length of the core and to the position of the core, also as to whether it is parallel to or at any angle up to a right angle to the longitudinal axis of the gelatinous explosive. However, I know that my invention has more or less effectiveness under any of the conditions and full protection of my invention demands coverage of all forms.

While I have described gelatinous explosives containing 50% or more nitroglycerine or equivalent, it will be understood that any material which colloids the nitrocellulose or equivalent and thus forms a gelatinous explosive is within the scope of my claims.

Since the invention resides in the thought of providing a core of a less gelatinous nature than the main body of the explosive and one more resistant to being converted into a massof high density under pressure, irrespective of the particular chemical composition of either the main body of explosive or the core, the invention goes even further than this in that it embodies the basic thought of providing. a core in a charge for shooting deep wells which will preserve its qualities of aeration under pressure and/or under temperature changes to better advantage than the main body of the explosive whether either of these materials is gelatinous or not, and I wish to make it clear that I claim as my invention any combination of materials constituting a complete explosivecharge likely to be adversely efiected by deep well pressures or other deep well conditions and wherein there is provided a separate propagation core of a nature to be more resistant to being rendered of high density under such deep well conditions, than the main body of the charge.

Iwill cite some field observations to indicate the great benefits resultant from my invention. By

the use of this cored gelatinous explosive the following points of superiority were observed in gas well blasting as compared to gelatinous explosives previously used in this work. That maximum explosive energy was obtained, was evidenced by the. unusually large pieces of rock which were thrown forcibly from the well hole; that the element of brisance, or shattering action, was greater was indicated by a spray of fine fiour-like dust which was brought out of the-well hole by the gas for several hours'following the shot; that the detonating wave propagated the entire length of the gelatinous explosive with a full rate of detonation was indicated by the steadily increasing volume of sound of the explosion; that a maximum volume of gas was generated by the explosive in a minimum amount of time was indicated by the increased height to which debris was thrown in the airby the explosion: that the a shock imparted to the gas bearing strata was greater was indicated by a perceptibly increased earth tremor from the explosion; that the detonation of the entire length of gelatinous explosive took place in a shorter length of time was indicated by the rapidity with which the gas cooled down from the heat of detonation after the explosion. The volume of natural gas produced from wells blasted by this cored gelatinous explosive was more than was expected when judgment was based on production obtained by previously used gelatinous explosives.

The field tests were carried on under the observation of men who have spent their lives in drilling, shooting and operating gas and oil wells, and the foregoing statements of improved re- 110 sults represent the result of their observations of these actual tests.

Having described my invention what I claim is:

1. An explosive of the character described comprising a main body of gelatinous dynamite, and 115 a core of less gelatinous dynamite therein, said core having a propagation sensitiveness material- -ly in excess of that of the main charge under the conditions of use.

2. An explosive of the character described comprising a main body of gelatinous dynamite, and a core of less gelatinous and more granular dynamite therein and extending entirely therethrough, said core having a propagation sensitiveness materially in excess of that of the main charge under the conditions of use. i

3. An explosive of the character described comprising a main body of gelatinous dynamite, and a core of less gelatinous and more granular dynamite therein and extending entirely therethrough, said core having a cross sectional area of approximately .196 sq. in.

4. A structure as recited in claim 1 wherein said core has a cross sectional area of approximately .196 sq. in.

5. An explosive assembly for deep well blasting comp-rising an outer body of main explosive consisting of a gelatin dynamite, and a propagation corehoused therein consisting of a dynamite having a higher propagation sensitiveness than a similar cross sectional area of the main explosive and wherein the porportions are such that the main explosive comprises at least 50% of the entire assembly.

6, A charge for deep well blasting comprising 14 a main body of gelatin dynamite and a core of straight nitroglycerine dynamite housed therein, said main body of gelatin dynamite having not less than 50% nitroglycerine content.

7. An explosive of the character described con- 1 taining a body of main high. explosive material and a core of explosive propagation material therein of a nature to maintain its qualities of aeration more effectively under pressure than the material of the main charge, said core being char-' acterized by its main sensitizer being a highly sensitive liquid organic nitrate of the order of nitroglycerine.

8. An explosive of the character described containing a body of main high explosive material and a core of explosive propagation material therein of a nature to maintain its qualities of aeration more efiectively under pressure than the material of the main charge, said corebeing characterized by having as its main sensitizer nitroglycerine.

9. An explosive of the character described comprising a body of main explosive of a gelatinous nature, and a propagation core of an explosive material of a less gelatinuous and more granular nature, said core being characterized by having as its main sensitizer a highly sensitive liquid organic nitrate whereby said core is rendered of higher propagation sensitiveness than the main explosive when used under pressure.

10. The herein described method of shooting deep wells which consists of exploding therein a charge consisting of a gelatinous main body of explosive, and a core of a less gelatinousand a more granular explosive, said core being characterized by its main sensitizer consisting of a highly sensitive liquid organic nitrate. whereby said core is rendered of higher propagation sensitiveness than the main explosive under the conditions of pressure existing in deep wells.

11. A gelatinous explosive containing 50% or more of a material which will gelatinize nitrocellulose and which explosive is provided with an insert of a non-gelatinous or semi-gelatinous granular explosive, said insert being characterized by having as its main sensitizer a highly sensitive liquid organic nitrate of the order of nitroglycerine, the said insert providing a propagating material having a higher propagation sensitiveness than the main explosive under conditions of pressure.

12. A self -propagating high explosive assembly comprising a body of main gelatinous high explosive containiing at least 50% of a liquid explosive material as described, which is gelatinizable by nitrocellulose, and an insert of high explosive propagation material, therein, of a nature to maintain its qualities of aeration more efiectively under pressure than the material of the main charge, said core containing as its main sensitizer an aliphatic liquid organic nitrate, the main gelatinous high explosive comprising at least onehalf of the entire assembly by weight.

JOHN M. JEFFRIES. 

